Adding SDK requires some special knowledge. If not used correctly it could lead to some bugs and conflicts in the code of your app. Source

Server-to-server or S2S conversion tracking enables customers to send the required details for AdWords app conversion tracking from their server to Google’s server at the time of the conversion event. SDKs aren’t as easy to incorporate into a mobile app as it might be to add a piece of code to a website. If not implemented correctly, adding the SDK and conversion tracking code could result in bugs in the app. Read more here: https://support.google.com/partners/answer/6209179